1. Field of the Invention
The present invention relates to devices used for carrying items and, more particularly, to wheel barrow type devices generally comprising a single wheeled vehicle having a bucket for holding refuse, cement, tools, etc.
2. Description of the Prior Art
Wheel barrows have been extensively used for carrying cement, refuse, tools and other such items. A basic wheel barrow device consists of a standard frame formed from a pair of generally straight frame members that converge toward a front portion of the device. A wheel is rotatably mounted to a bottom of the frame members at the converged front portion of the device. A bucket is mounted on top of the frame members rearwardly from the front portion at which the wheel is mounted. The diverging rear portions of the frame members form handles for lifting and guiding the wheel barrow. V-shaped supports are generally provided on the bottom side of the frame members below the bucket for supporting the rear portion of the wheel barrow so that the bucket remains substantially parallel to the ground when at rest.
A typical wheelbarrow is arranged such that when it is being pushed a substantial portion of the weight of the load in the bucket is pivoted and balanced over the wheel. This enables an operator of the wheel barrow to push and guide the wheel barrow without bearing the entire weight of the load.
A large wheel barrow, that is a wheel barrow having a large bucket, can carry several hundred pounds of refuse or material. On smooth, level or slightly downhill grades, a fully loaded wheel barrow is fairly easy to maneuver, although the initial force necessary to set the wheel barrow in motion may be great. However, when a fully loaded wheel barrow is used on rough or uphill grades, it is often difficult to keep the wheel barrow in motion and an operator pushing the wheel barrow must expend a large amount of energy. On the other hand, on large downhill grades the opposite is true and it is often difficult to slow the wheel barrow down to a speed at which it is easy and safe to control the wheel barrow.
Various approaches have been taken to provide a power-driven wheel barrow for removing some of the burden involved with moving a wheel barrow over rough or uneven terrain. Several approaches involve adding a motor and a simple direct chain or belt between the motor and the drive wheel of the wheel barrow for providing a drive force for moving the wheel barrow. However, these approaches generally involve the use of lengthy chains or belts or in some cases, the use of several chains or belts. One disadvantage of such approaches is that debris often interferes with the drive mechanism making the operation and maintenance of the device difficult. In addition, relatively large and heavy engines are generally used in such approaches and this adds significantly to the overall weight of the wheel barrow. Also, such direct drives often do not allow the motor to be disengaged from the main drive wheel and the wheel barrow can not be used as an ordinary push-type wheel barrow. This is particularly inconvenient when the load being carried is light weight and does not necessitate the power drive. In addition, since the only practical location to place the relatively heavy engine and drive mechanism is below the bucket and behind the main wheel, the extra weight of the engine and drive mechanism may not be conveniently pivoted and balanced over the main wheel when an operator is pushing the wheel barrow. Accordingly, the operator must bear the burden of carrying the extra weight of the engine and drive mechanism.
Several prior art approaches involve adding extra wheels to a rear of the wheel barrow to relieve some of the burden on the operator from having to carry the added weight. However, since it is often required to use the wheel barrow in confined areas or even on a narrow plank or path, such multi-wheeled wheel barrows have limited utility.
Another approach is discussed in U.S. Pat. No. 4,589,508 and consists of a motorized wheel barrow including a friction drive transmission. The friction transmission consists of a friction wheel driven by an engine by use of a chain and sprockets. The friction wheel rotates in a clockwise direction in a horizontal plane. The friction wheel is movable to the right and left to engage either one of two friction drive plates provided one on either side of the friction wheel. The drive plates are connected to each other through an intermediate cylinder and a sprocket is attached to an outside end of one of the drive plates for driving a chain attached to the main drive wheel of the wheel barrow. When the friction wheel is moved to the right, it engages one of the drive plates and the sprocket on the drive plate assembly and the main drive wheel of the wheel barrow are rotated in a first direction. When the friction wheel is moved to the left, it engages the other drive plate and the sprocket on the drive plate assembly and the main drive wheel of the wheel barrow are rotated in a direction opposite to the first direction.
However, since wheel barrows are often used in an environment that is wet, muddy or dirty, one disadvantage of such a friction drive transmission is that if the drive plates get wet or get some other debris on them, the friction wheel may slip which could cause a sudden loss of drive to the main drive wheel. A sudden loss of drive to the main drive wheel, particularly when climbing an uphill grade, could cause loss of control and cause the load in the wheel barrow to shift and cause spilling of the load or even injury. In addition, since the relatively heavy engine and extra gearing required by such a friction drive device add considerably to the overall weight of the device, it is difficult to tip the entire wheel barrow. Accordingly an arm is provided for manually lifting just the bucket to enable manual dumping of the contents of the bucket without having to lift the engine. This requires even more hardware and further modifications to the wheel barrow adding to the overall cost and weight of the device.